Selective alkylation of phenol



United States Patent 3,423,474 SELECTIVE ALKYLATION 0F PHENOL Robert Grirlin Anderson, Terra Linda, and Samuel H.

Sharman,*Kensington, 'Calif., assignors to Chevron Research Company, a corporation of Delaware No Drawing. Filed May 28, 1965, Ser. No. 459,937 US. Cl. 260624 3 Claims Int. Cl. C07c 39/06 ABSTRACT OF THE DISCLOSURE Selective alkylation of phenol with a l-alkene under non-catalytic conditions, elevated temperatures and short reaction times thereby producing alkylphenols in which the benzene ring is attached to the 1- or Z-position of the alkyl chain.

This invention relates to a method for the production of monoalkyl substituted phenols. More particularly, it relates to an improved method for the selective production of higher molecular weight alkyl phenols in which the attachment of the hydroxyphenyl radical to the alkyl side chain is predominantly at an alkyl chain end-section, v1z.,

Alkyl substituted phenols are known and used in the art, and for many purposes the characteristic product resulting from conventional production processes is a satis factory material. In some uses, however, and in particular in its use as a precursor for detergent production, it is now found to be unsatisfactory. The principal defect is the position isomer distribution relative to the situs of the phenol radical attachment to the higher alkyl chain.

The conventional product, in general, is found to contain from about 25 to 60 mole percent of the hydroxyphenyl groups internally bonded, that is, non-end-section bonded, to the alkyl side chain. The larger percentages correspond to the higher molecular weight alkyl side chains. In no case using conventional process means does it appear possible in a practical manner to produce monoalkylphenols having a preponderance of hydroxyphenyl attachment at the 1- and 2-positions (i.e., the end section) of the alkyl chain in a higher alkyl substi tuted phenol.

It has now been found that alkyl substituted phenols of the general formula can be produced, wherein R is a saturated hydrocarbon radical having from 4 to about 17 carbon atoms and Y is a hydroxyphenyl radical, from an alkylation of phenol by a l-alkene of the general formula wherein R is defined as above by heating a mixture of phenol and the l-alkene at a temperature in the range from about 650 F. to 900 F. for a period in the range from about one to one hundred minutes provided that the reactant-product density in the reaction zone is not less than about 0.2 gram per cubic centimeteL'The ratio of phenol to l-alkene in the mixture should be in the range from about 0.1 to moles of phenol per mole of l-alkene.

Under the foregoing conditions the resulting product is at least 90 percent of the desired alkyl end-section attachment type of alkylphenol. The position of attachment of the side chain on the aromatic ring is predominantly ortho to the hydroxyl group. When, however, reaction times are excessive and/or the reactant-product 3,423,474 Patented Jan. 21, 1969 density is appreciably less than about 0.2 gram per cubic centimeter, the resulting product is substantially the unsatisfactory internally attached alkylphenol.

By reactant-product density is meant the sum of the weights of phenol, l-alkene and resulting alkylphenol per unit volume.

In a preferred mode of the process, the alkylation is accomplished at a temperature in the range from about 700900 F. in a continuous process at a pressure suflicient to maintain the reactantproduct density about 0.2 gram per cubic centimeter. Except for the case of the higher l-alkenes, the reactants will be above their critical temperatures, and thus elevated pressures of the order of 20-80 atmospheres are required to ensure the maintenance of reactant-product densities as noted above.

In the above preferred continuous process a mixture of phenol and l-alkene in the mole ratio of from about 1:1 to 3:1, respectively, is heated for the desired reaction period. The reaction is then quenched by cooling or by a flash distillation at subreaction pressures, with the unconverted feed being recycled to the reaction zone and the alkylphenol further fractionated for ultimate use.

When the process is carried out at lower temperatures, for example, in the temperature range from about 650 F. to 700 F., batch-type reactors can be employed, but the reaction times are longer; consequently, production rates per unit volume of reactor are lower. A counterbalancing advantage, however, is that high pressure equipment is not required at the lower end of this range.

Permissible reaction periods for the production of a satisfactory alkylphenol, i.e., at least of the 1- or 2-alkyl type, vary depending upon the temperature. At about 650 F. a period less than about minutes is suitable. At 900 F. the period should be less than 1 minute. At intermediate temperatures, the maximum permissible reaction time will be proportionately intermediate one minute and one hundred minutes.

In general, the pressure required to maintain suitable reactant product densities will vary depending upon the temperature, the feed, the higher l-alkene, i.e., C -C l-alkenes, and the relative amount of phenol. The maximum pressure required will be that of about 80 atmospheres for the l-heptene and phenol system. For higher molecular weight alkenes the pressure needed will be less.

Relative molar amounts of phenol to l-alkene in excess of 13:1, respectively, can be used. At least a 1:1 ratio is desirable; otherwise, a substantial amount of undesirable polyalkylation of the phenol results thereby sacrificing feed to by-products and complicating product purifications. The use of phenol to l-alkene mole ratios above about 6 to l are relatively inefficient in that the burden of separation and recycle together with non productive use of reactor volume out-weighs the advantages of the use of high phenol ratios for the inhibition of polyalkylation.

The alkenes useful in the alkylation of phenol in the process are all l-alkenes. The n-l-alkenes are preferred. However, l-alkenes of the general formula wherein R is a univalent radical derived from a saturated aliphatic hydrocarbon by the removal of a single hydrogen atom and having from 4 to about 17 carbon atoms may be employed for the production of the particular alkyl substituted phenols characterized above. Thus R may be straight, and branched chains, cyclic, i.e., alkyl, cycloalkyl, alkylcycloalkyl, and cycloalkylalkyl.

Representative l-alkenes include l-dodecene, l-hepten, l-octene, l-undecene, l-eicosene; 4,4-dimethyl-1- octene, S-ethyl-l-hexadecene, 4,5-dimethyl-1-decene, 6-

methyl-l-heptene, 6-methyl-1-nonene; 4-cyclohexyl-1- butene, S-cyclopentyl-l-pentene, S-cyclooctyl-l-pentene, d-cyclododecyl-l-hexene and the like l-alkenes. In particular n-l-alkene fractions and mixtures thereof as derived from the non-catalytic vapor phase cracking of petroleum wax fractions are preferred feeds to the subject process.

The following examples will serve to illustrate the invention but they are not to be considered as limiting.

EXAMPLE 1 Into a pressure autoclave, phenol and l-nonene were charged in a mole ratio of 2.7 to 1, respectively. Sufficient vapor space was allowed for expansion. The reactor and contents were heated and maintained at 700 F., while maintaining the reactant-product density substantially above 0.2 gram per cubic centimeter, for the period and with the results as follows.

Product, percent Time, hrs.: end section MAP 0.5 97 2.0 82 4.0 78

Monoalkylphenol, 'the sum of l-alkylphenol plus 2-alkyl phenol divided by total monoalkylphen-ol times 100.

The product analyses were made by the use of vapor phase chromatographic techniques using appropriate standards.

EXAMPLE 2 Example 1 was repeated at 800 F.

Product, percent Time, hrs.: end section MAP 0.025 93 0.13 85 wherein t=time in minutes and T=reaction temperature in degree Fahrenheit. Slightly longer reaction times may be employed and yet obtain a product which is at least 80% of end section attached monoalkylphenol.

EXAMPLE 3 The alkylation of phenol using l-nonene was repeated at 700 F. under analogous conditions except that in Run A the reactant-product density was about 0.3 and in Run B it was about 0.04 gram per cubic centimeter. The results found were:

Conversion, Percent end secpercent tion MAP 1 l Monoalkylphenol, 1- and 2- isomers.

These data illustrate that reaction in a dilute phase must be avoided if satisfactory production of 1- and 2- alkyphenol is to be achieved. Thus, where critical temperatures are exceeded, sufficient pressure must be applied to the reaction system to insure a reactants-product density sufficiently above about 0.2 gram per cubic centimeter in order that undesirable secondary-dilute phase reactions are inhibited.

EXAMPLE 4 In a continuous reaction system phenol and a l-nonene/l-decene mixture (average molecular weight of 136) are premixed in a feed line, and then introduced into a reaction zone maintained at about 800 F. The hourly feed rate is as follows: (1) phenol at 597 lbs. and (2) the l-alkene mixture at 903 lbs. The residence time is 0.07 hour. A pressure of about 68 atmospheres is applied in the reaction zone in order to maintain the reactantsproduct density above 0.2 gram per cubic centimeter.

The resulting reaction product mixture is then introduced into a stripping still maintained at about one atmosphere pressure. The product is flash distilled in the still. Except for a bleed stream (for the prevention of by-product buildup) of about 46 lbs., the overhead fraction comprising unconverted phenol and l-alkene, 9180 lbs., is recycled to the reactor. The bottoms which is mainly the desired monoalkyl substituted phenol is withdrawn and fractionated in a second distillation column yielding about 1250 lbs. of predominately endchain attached alkyl phenol and about 204 lbs. of bottoms which is mainly dia-lkyl substituted phenol.

Essentially analogous results are obtained when any of the prescribed l-alkenes or mixtures thereof are used in the foregoing continuous process.

Clearly, modifications and variations of the invention as hereinbefore set forth and exemplified may be made Without departing from the sense thereof. Therefore, only such limitations should be imposed as are indicated in the appended claims.

We claim:

1. In a process for the production of a monoalkyl substituted phenol by heating a mixture of phenol and a l-alkene of the formula:

RCH CH=CH in which R is a univalent radical derived from a saturated aliphatic htydrocarbon by the removal of a single hydrogen atom and containing from 4 to 17 carbon atoms, and mixtures thereof; wherein the mole ratio of phenol to alkene in said mixture is in the range from about 0.1 :1 to 10:1, the improvement which comprises heating said mixture at a temperature in the range from 700 F. to 900 F. for a time not greater than that defined by the equation log t:

wherein R is defined as above and Y is a radical selected from the group consisting of o-hydroxyand p-hydroxyphenyl.

2. The process as in claim 1 wherein said l-alkene is a normal l-alkene.

3. The process as in claim 1 wherein said reaction temperature is in the range 700900 F., and said mole 3,423,474 5 6 ratio of phenol to l-alkene is in the range from about FOREIGN PATENTS respective 746,407 3/1956 Great Britain.

References Cited UNITED STATES PATENTS 5 LEON ZITVER, Primary Exammer. 2,161,826 6/1939 Kyrides et a1 260-624 LONE, Assistant Examiner- 

